The disclosure relates to pumps. More particularly, the disclosure relates to gear pumps used in compressor lubrication.
Compressors such as reciprocating compressors require lubrication. An exemplary reciprocating compressor can require lubrication at one or more of several locations. These locations include main bearings supporting a shaft relative to the case. For reciprocating compressors, the shaft is a crankshaft and the locations further include: bearings between the crankshaft and rods; wrist bearings of the rods/pistons; and the piston/cylinder interfaces. Oil may be delivered through passageways in the shaft. An oil pump may be mounted to be driven by the shaft to draw oil from a compressor sump and drive it through the passageways.
An exemplary pump is sold as the “TR Series Pump” by Tuthill Pump Group of Alsip, Ill., US. Such pump has an externally lobed idler (inner gerotor gear) mounted within an internally-lobed rotor (outer gerotor gear). The rotor is a portion of a rotor/torque ring assembly. The torque ring comprises a sleeve within which the rotor is secured (e.g., by welding, interference fit, or the like). As is discussed below, the torque ring drives rotation of the rotor and, via the rotor rotation of the idler.
Respective first and second end portions of the torque ring protrude beyond opposite first and second ends of the rotor. The first end portion is a proximal end portion and mounts to the crankshaft to be rotated about the crank axis. The first end portion also floating plate or washer that serves as a pressure relief valve element. The washer is biased by a spring into sealing engagement with the first ends of the rotor and idler. A forward portion of the spring may be in a sealing sleeve slidingly mounted in the spring compartment of the crankshaft.
The second end portion contains a carrier assembly that comprises a hollow axle on which the idler rides. The axle has an axis parallel to and slightly offset from the crank axis. The carrier assembly has an end plate from which the axle protrudes. The end plate is mounted to the second end portion of the rotor/torque ring.
The exemplary pump is an automatic reversing pump that provides flow in on flow direction regardless of the direction of shaft rotation. This is achieved by providing the end plate with a pair of ports that interact with a pair of ports of a pump cover. The pump cover ports are a respective inlet port and outlet port. The cover inlet port is in communication with an oil pickup line extending to an inlet (e.g., at a strainer in the compressor sump). The cover outlet port is in communication with a bore of the axle to pass flow through passageways in the crankshaft to bearings.
As rotation of the ring drives rotation of the idler pockets formed between their lobes will sequentially be open to the two cover ports via the two carrier ports. The pockets will open to the cover inlet port, expand to draw liquid in from the cover inlet port, close to the cover inlet port and open to the cover outlet port, contract so as to discharge liquid through the cover outlet port, and then close to the cover outlet port and open to the cover inlet port to complete the cycle,
If pressure in the pocket becomes sufficient to overcome the spring bias, the pressure will shift the washer out of sealing contact with the ends of the idler and rotor and open up a pathway for fluid to pass back through the cover inlet to relieve pressure.